This invention relates to saddle inserters utilizing rotating drums for extracting a signature and opening the signature into an inverted "V" shape for placement on a saddle gatherer prior to binding. The signatures, in the simplest form, are single sheets of paper folded in the middle so as to constitute four paper surfaces and may range to sixteen or more such sheets. Before the pages of the signatures can be bound, the halves, or laps, on the opposite sides of the fold must be spread so that the signatures can be assembled together and the folds of the signatures can be stapled or stitched.
In accomplishing this, grippers on an extractor cylinder or drum grip the endmost signature in a hopper by the folded edge and carry the signature around the drum to a stop position. When the signature is in position on the extractor drum, an oscillating "dipper" approaches the signature from the side toward the extractor drum and picks up the cut end of the signature and supports it so that grippers may grip it.
Grippers on a transfer drum then grip the lower cut end of the signature, pull it away from the extractor drum and carry it to an opener drum. As the folded signature descends between the opener and transfer drums, each half of the signature is clamped by means of vacuum and/or mechanical grippers associated with the drums. As the drums rotate in opposite directions, the signature laps are opened into an inverted "V" and released onto a saddle from which it is gathered together with other signatures and delivered to a saddle stitching machine for stapling.
When a signature is in the stop position on the extractor drum the cut or lapped edge of the signature must be contained so that the dippers can position it for grippers on the transfer drum to grip the lapped edge in preparation for carrying the signature around the transfer drum to the opener drum. Heretofore, such containing has been provided by a roller of relatively small diameter compared to that of the extractor and transfer drums positioned just above the nip between the two drums. An arrangement of this type is disclosed in U.S. Pat. No. 3,692,300.
While the roller performs the basic function of containing a signature, it also imposes upon the signature a rather severe and tortuous path in its travel from the extractor drum to the transfer drum.
Further, the cut edge of a signature tends to be deflected away from the dippers when first contacted thereby. Because of the small diameter of the roller and its close position to the nip between the extractor drum and transfer drum, the cut end of the signature below the roller may be deflected sharply when contacted by the dipper and tend to curl upwardly. In some cases the cut edge of the signature is gripped while in this condition which produces a fold at the cut edge with consequent malfunctions and paper jams.